This invention relates generally to thruster systems used for maneuvering a marine vessel. More specifically, this invention relates to an improved thrust director unit for use in a thruster system, to achieve energy-efficient generation of a directionally adjustable water jet flow used to maneuver and/or propel the marine vessel.
Boat thruster systems are generally known in the art for use in close-quarter maneuvering of a marine vessel. Such thruster systems are designed to generate a flow of water discharged below the water line from one side of a boat hull, resulting in a substantial hydraulic reaction force applied to the vessel for improved close-quarter maneuvering. In one traditional form, the thruster system comprises a relative large diameter propeller mounted within a correspondingly sized transverse opening or tunnel formed in a boat hull, wherein the propeller is adapted to generate a substantial mass flow of water directed to one side of the vessel in accordance with the direction of propeller rotation. While so-called tunnel thrusters of this type provide significant advantages in close-quarter vessel maneuvering, especially upon approach to or departure from a dock, the tunnel thruster system occupies a large volumetric space within the hull of the vessel. Moreover, large openings must be formed in the vessel's hull, usually in a dry dock environment, to accommodate installation of the requisite large diameter flow tunnel. As a result, tunnel thruster systems exhibit significant disadvantages with respect to system size and installation costs.
In recent years, alternative and comparatively more compact thruster systems have been designed wherein a high capacity water pump delivers water for discharge as a high velocity flow jet or jets through relatively small nozzles mounted at opposite sides of the vessel's hull. See, for example, U.S. Pat. Nos. 4,056,073; 4,214,544; 4,455,960; and 5,289,793. In these thruster systems, the pump draws in water through an open intake formed in the hull, and the water is delivered through a diffuser and directionally controlled vanes for discharge flow through one or more of the hull nozzles, resulting in an hydraulic reaction force which is effective to assist in vessel maneuvering. Thrust director units having adjustable vanes are often employed at the discharge nozzles for directionally adjusting the water jet flow in a sideward direction to generate a sideward thrust, or in a forwardly or rearwardly angled direction to respectively produce a reverse or forward propulsion thrust. In this regard, such thrust director units have typically included nozzle housings formed with diverging fore and aft walls to accommodate directional jet flow adjustment through a range of forwardly angled to rearwardly angled directions. Such nozzle housing geometries, of diverging configuration, have thereby tended to permit the discharged jet flow to diverge and diffuse such that there is substantial energy inefficiency particularly when vanes are set in a sideward thrust position.
The present invention provides a significant improvement upon thrust director units used in marine thruster systems, by providing a nozzle housing geometry of diverging shape to accommodate adjustable direction discharge of the water jet flow, but wherein deflector vanes cooperate with the nozzle housing to define a discharge flow path of nondiverging cross sectional shape.